1. Field of the Invention
The present invention concerns floor polishing machines and in particular floor polishing machines with only one brush wheel rotating about a vertical axis.
2. Description of Related Art
At present, to polish the floor of houses, offices, laboratories, etc. polishing machines are used which are equipped with a horizontal polishing wheel comprising a rigid or semi-rigid rotary plate on which a layer of elastic material and a layer of soft polishing material, for example, felt, are applied. These machines are provided with a front castor and two rear, non-swivelling wheels that support the weight of the machines. During transport, a polishing wheel is completely raised from the floor and the rear wheels make it possible to transport a machine even on rough floors. During use, all the wheels rest on the floor and the pressure of the polishing wheel against the floor is obtained by adjusting the height of the front castor. One of the drawbacks of such a machine is that it is not possible to obtain an even contact of the polishing wheel with the floor. In fact, the contact is only partial, due to the inclination caused by the front castor. In some cases an adjustable castor is used at the center of the polishing wheel and the pressure against the floor adjusted either manually or by means of thrust springs. In both cases, the contact of the polishing wheel is even, however, to avoid excessive current usage in the operation of the machine, it is necessary to reduce the force against the floor, thus reducing the polishing action as well.
These known floor polishing machines present other drawbacks such as upon starting, the polishing wheel must overcome static friction, therefore the motor requires more electric current and this results in unacceptable consequences when considering the technical specifications required by users and by regulations in force. Furthermore, in certain situations, the load placed on an electrical circuit may cause circuit breakers to interrupt electric energy flow to other equipment like computers, machine tools, etc. Also, if the polishing wheel meets an obstacle on the floor, such as an unevenness of the floor, badly jointed marble slabs, expansion joints between different kinds of floors, its rotational speed is reduced and a greater load is place on the motor requiring an increase in electric energy consumption. Further, although it is possible to adjust the pressure exerted by the polishing wheel on the floor, the position of the polishing wheel with respect to the floor is often inclined and therefore the friction of the polishing wheel on the floor is not proper and the polishing action is reduced. Therefore, the operator must notice if the pressure exerted by the polishing wheel is insufficient or excessive, checking if the floor on which the machine has just passed is polished (insufficient pressure, considerable presence of wax on the floor) or if the motor rotates with difficulty and the machine resists its own advancement (excessive pressure, sticking of the polishing wheel to the wax on the floor).